用直流电压降法研究316LN不锈钢的疲劳裂纹扩展行为

Research on Fatigue Crack Growth Behavior of 316LN Stainless Steel by Direct Current Potential Drop Method

采用直流电压降（DCPD）方法测试了316LN不锈钢在室温和350℃的疲劳裂纹扩展速率,得到室温和350℃下该材料疲劳裂纹扩展门槛值ΔKth,并分析了试样断口形貌。结果表明：采用DCPD方法测得室温和350℃下ΔKth分别为11.9,8.1MPa·m^1/2,与文献值相符,350℃下的疲劳裂纹扩展速率比室温下的要高2～20倍;在裂纹亚临界扩展区,疲劳裂纹扩展速率与应力强度因子范围服从Paris公式,其参数n与温度无关,参数D与温度成线性正比关系;试样疲劳破坏形式为穿晶断裂。

Fatigue crack growth rates of 316LN stainless steel at room temperature and 350 ℃ were measured by the direct current potential drop （DCPD） method, and then the fatigue-crack growth threshold （△Kth） at room temperature and 350 ℃ was obtained. The fatigue fracture morphology was also analyzed. The results show that the △Kth obtained by the DCPD method at room temperature and 350 ℃ was 11.9, 8.1 MPa·m^1/2 respectively, coinciding well with the values from references. The fatigue crack growth rates at 350 ℃ were about 2-20 times as high as those at room temperature. In the subcritical propagation zone, the relationship between fatigue crack growth rate and stress intensity factor range accorded with Paris equation. The parameter m in the equation was temperature-independent while parameter D showed a linearly positive correlation with temperature. The failure mode of the specimen was transgranular fracture.